As mobile devices have been increasingly developed and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased as an energy source for the mobile devices. Among such secondary batteries is a lithium secondary battery having high energy density and discharge voltage, into which much research has been carried out and which is now commercially and widely used.
Based on the shape of a battery case, a secondary battery may be classified as a cylindrical battery having an electrode stack mounted in a cylindrical metal can, a prismatic battery having an electrode stack mounted in a prismatic metal can, or a pouch-shaped battery having an electrode stack mounted in a pouch-shaped battery case made of an aluminum laminate sheet. Thanks to the shape-related characteristics thereof, the cylindrical battery is used in various kinds of devices.
In general, the electrode stack mounted in the cylindrical battery functions as a power generating element having a positive electrode/separator/negative electrode stack structure that can be charged and discharged. The electrode stack mounted in the cylindrical battery is configured as a jelly-roll type electrode stack configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode, to which active materials are applied, are wound around a core in the state in which a separator is disposed between the positive electrode and the negative electrode.
The jelly-roll type electrode stack has advantages in that it is possible to easily manufacture the jelly-roll type electrode stack and in that the jelly-roll type electrode stack has high energy density per unit weight.
In the case in which a middle or large-sized battery is manufactured using the cylindrical battery, however, it is difficult to discharge heat generated in the middle part of the cylindrical battery to the outside. When the cylindrical battery is repeatedly charged and discharged, therefore, the middle part of the cylindrical battery repeatedly heats up, with the result that the life span of the secondary battery may be reduced. Furthermore, the secondary battery may easily catch fire or explode.
Therefore, there is a high necessity for a cylindrical battery having improved cooling performance.